How do hydraulic flat tappet lifters fail?

I think I just might do that. It's a bummer that this happened, but these are lessons I need to learn. Hell, a year ago I didn't know any of this, and quite honestly I'm kinda just proud that I put together an engine and made it run. It didn't run for long, but it ran and it was a hell of a lot of fun. As long as I don't repeat the same mistakes but instead learn from them, I think I'm good to go.